The invention disclosed herein is a device for adhering elastic bands to a moving sheet, such as the liquid impervious backing sheet of disposable diapers, and for folding the laterally spaced apart margins of the sheet over the bands to effect adhesion.
As is well known, disposable diapers are fabricated in the form of a continuous moving web which is finally cut at regular intervals to produce individual diapers. cut at regular intervals to produce individual diapers. Typically, the web is comprised of a liquid impervious backing sheet which is commonly a plastic such as polyethylene. A layer of absorbent material such as wood fiber fluff is deposited on the sheet within the area of each diaper. A porous sheet of non-woven material is superimposed over the absorbent material and glued at its edges to the backing sheet. At some stage of the fabrication process, stretched elastic bands are applied and adhered to the backing sheet. Usually this is the first step in the process. The elastic bands contract when the individual diapers are severed and are effective to cause the edges or margins of the diaper to fit snugly against the legs and buttocks of an infant when a diaper is applied.
One type of diaper has its laterally spaced apart side margins cut away in the central region of the diaper to give it an hourglass configuration. A narrow central region thus produces less bulkiness in the crotch region of the infant. In this type of diaper, the prestretched elastic band segments are parallel with each other and extend longitudinally over the crotch region. Typically the elastic bands are about three-sixteenths of an inch wide and about one-thirty-second of an inch thick which may be considered a standard for the industry.
Another type of diaper, which is marketed as an alternative to the more expensive type just described, has no contoured crotch but is rectangular. In rectangular diapers, the elastic bands are applied to the laterally spaced apart side margins of the backing sheet and the flaps or edges of the margins beyond the bands are folded over and adhered to conceal the bands and impart the elasticity of the bands to the margins of the backing sheet for effecting a snug fit on the infant. The practice has been to score and split the three-sixteenths band longitudinally to produce two bands of half the width of the original and to apply hot melt glue directly to these narrower bands and then fold the lateral margins of the moving backing sheet over them and let the glue set. Depositing a coating of glue on opposite sides of a very thin and narrow elastic band is difficult to control properly because the delicate band has a tendency to shift out of alignment when it experiences the pressure of a glue nozzle on it. It is difficult to prevent some glue from missing the band if a spray nozzle is used. There is also a problem with depositing too little or too much glue on the band.